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Add support for mbedtls 3.X.Y
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Most struct fields in mbedtls 3 are private and now need accessor
functions. Most of it was straightforward to adapt, but for two things
there were no accessor functions yet:

 * Netscape certificate type
 * key usage (you can check key usage, but not get the raw bytes)

I decided to remove Netscape certificate type checks when using OpenVPN
with mbedtls. The key usage bytes were printed in an error message, and
I removed that part from it.

Adding the random number functions to the load private key function may
look weird, but the purpose is to make side channels for elliptic curve
operations harder to exploit.

Change-Id: I445a93e84dc54b865b757038d22318ac427fce96
Signed-off-by: Max Fillinger <[email protected]>
Acked-by: Frank Lichtenheld <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg27295.html
Signed-off-by: Gert Doering <[email protected]>
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@mfil @cron2
mfil authored and cron2 committed Oct 29, 2023
1 parent 5b08891 commit ace7a4f
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Showing 6 changed files with 322 additions and 95 deletions.
10 changes: 8 additions & 2 deletions configure.ac
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1016,15 +1016,21 @@ elif test "${with_crypto_library}" = "mbedtls"; then
#include <mbedtls/version.h>
]],
[[
#if MBEDTLS_VERSION_NUMBER < 0x02000000 || MBEDTLS_VERSION_NUMBER >= 0x03000000
#if MBEDTLS_VERSION_NUMBER < 0x02000000 || (MBEDTLS_VERSION_NUMBER >= 0x03000000 && MBEDTLS_VERSION_NUMBER < 0x03020100)
#error invalid version
#endif
]]
)],
[AC_MSG_RESULT([ok])],
[AC_MSG_ERROR([mbed TLS 2.y.z required])]
[AC_MSG_ERROR([mbed TLS version >= 2.0.0 or >= 3.2.1 required])]
)

AC_CHECK_HEADER(
psa/crypto.h,
[AC_DEFINE([MBEDTLS_HAVE_PSA_CRYPTO_H], [1], [yes])],
[AC_DEFINE([MBEDTLS_HAVE_PSA_CRYPTO_H], [0], [no])]
)

AC_CHECK_FUNCS(
[ \
mbedtls_cipher_write_tag \
Expand Down
67 changes: 40 additions & 27 deletions src/openvpn/crypto_mbedtls.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@
#include "integer.h"
#include "crypto_backend.h"
#include "otime.h"
#include "mbedtls_compat.h"
#include "misc.h"

#include <mbedtls/base64.h>
Expand Down Expand Up @@ -170,10 +171,11 @@ show_available_ciphers(void)
while (*ciphers != 0)
{
const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(*ciphers);
if (info && !cipher_kt_insecure(info->name)
&& (cipher_kt_mode_aead(info->name) || cipher_kt_mode_cbc(info->name)))
const char *name = mbedtls_cipher_info_get_name(info);
if (info && name && !cipher_kt_insecure(name)
&& (cipher_kt_mode_aead(name) || cipher_kt_mode_cbc(name)))
{
print_cipher(info->name);
print_cipher(name);
}
ciphers++;
}
Expand All @@ -184,10 +186,11 @@ show_available_ciphers(void)
while (*ciphers != 0)
{
const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(*ciphers);
if (info && cipher_kt_insecure(info->name)
&& (cipher_kt_mode_aead(info->name) || cipher_kt_mode_cbc(info->name)))
const char *name = mbedtls_cipher_info_get_name(info);
if (info && name && cipher_kt_insecure(name)
&& (cipher_kt_mode_aead(name) || cipher_kt_mode_cbc(name)))
{
print_cipher(info->name);
print_cipher(name);
}
ciphers++;
}
Expand Down Expand Up @@ -295,7 +298,9 @@ crypto_pem_decode(const char *name, struct buffer *dst,
mbedtls_pem_context ctx = { 0 };
bool ret = mbed_ok(mbedtls_pem_read_buffer(&ctx, header, footer, BPTR(&input),
NULL, 0, &use_len));
if (ret && !buf_write(dst, ctx.buf, ctx.buflen))
size_t buf_size = 0;
const unsigned char *buf = mbedtls_pem_get_buffer(&ctx, &buf_size);
if (ret && !buf_write(dst, buf, buf_size))
{
ret = false;
msg(M_WARN, "PEM decode error: destination buffer too small");
Expand Down Expand Up @@ -416,11 +421,12 @@ cipher_valid_reason(const char *ciphername, const char **reason)
return false;
}

if (cipher->key_bitlen/8 > MAX_CIPHER_KEY_LENGTH)
const size_t key_bytelen = mbedtls_cipher_info_get_key_bitlen(cipher)/8;
if (key_bytelen > MAX_CIPHER_KEY_LENGTH)
{
msg(D_LOW, "Cipher algorithm '%s' uses a default key size (%d bytes) "
msg(D_LOW, "Cipher algorithm '%s' uses a default key size (%zu bytes) "
"which is larger than " PACKAGE_NAME "'s current maximum key size "
"(%d bytes)", ciphername, cipher->key_bitlen/8, MAX_CIPHER_KEY_LENGTH);
"(%d bytes)", ciphername, key_bytelen, MAX_CIPHER_KEY_LENGTH);
*reason = "disabled due to key size too large";
return false;
}
Expand All @@ -438,7 +444,7 @@ cipher_kt_name(const char *ciphername)
return "[null-cipher]";
}

return translate_cipher_name_to_openvpn(cipher_kt->name);
return translate_cipher_name_to_openvpn(mbedtls_cipher_info_get_name(cipher_kt));
}

int
Expand All @@ -451,7 +457,7 @@ cipher_kt_key_size(const char *ciphername)
return 0;
}

return cipher_kt->key_bitlen/8;
return (int)mbedtls_cipher_info_get_key_bitlen(cipher_kt)/8;
}

int
Expand All @@ -463,7 +469,7 @@ cipher_kt_iv_size(const char *ciphername)
{
return 0;
}
return cipher_kt->iv_size;
return (int)mbedtls_cipher_info_get_iv_size(cipher_kt);
}

int
Expand All @@ -474,7 +480,7 @@ cipher_kt_block_size(const char *ciphername)
{
return 0;
}
return cipher_kt->block_size;
return (int)mbedtls_cipher_info_get_block_size(cipher_kt);
}

int
Expand All @@ -498,16 +504,16 @@ cipher_kt_insecure(const char *ciphername)

return !(cipher_kt_block_size(ciphername) >= 128 / 8
#ifdef MBEDTLS_CHACHAPOLY_C
|| cipher_kt->type == MBEDTLS_CIPHER_CHACHA20_POLY1305
|| mbedtls_cipher_info_get_type(cipher_kt) == MBEDTLS_CIPHER_CHACHA20_POLY1305
#endif
);
}

static int
static mbedtls_cipher_mode_t
cipher_kt_mode(const mbedtls_cipher_info_t *cipher_kt)
{
ASSERT(NULL != cipher_kt);
return cipher_kt->mode;
return mbedtls_cipher_info_get_mode(cipher_kt);
}

bool
Expand Down Expand Up @@ -566,22 +572,29 @@ cipher_ctx_init(mbedtls_cipher_context_t *ctx, const uint8_t *key,
CLEAR(*ctx);

const mbedtls_cipher_info_t *kt = cipher_get(ciphername);
int key_len = kt->key_bitlen/8;

ASSERT(kt);
size_t key_bitlen = mbedtls_cipher_info_get_key_bitlen(kt);

if (!mbed_ok(mbedtls_cipher_setup(ctx, kt)))
{
msg(M_FATAL, "mbed TLS cipher context init #1");
}

if (!mbed_ok(mbedtls_cipher_setkey(ctx, key, key_len*8, operation)))
if (!mbed_ok(mbedtls_cipher_setkey(ctx, key, (int)key_bitlen, operation)))
{
msg(M_FATAL, "mbed TLS cipher set key");
}

if (mbedtls_cipher_info_get_mode(kt) == MBEDTLS_MODE_CBC)
{
if (!mbed_ok(mbedtls_cipher_set_padding_mode(ctx, MBEDTLS_PADDING_PKCS7)))
{
msg(M_FATAL, "mbed TLS cipher set padding mode");
}
}

/* make sure we used a big enough key */
ASSERT(ctx->key_bitlen <= key_len*8);
ASSERT(mbedtls_cipher_get_key_bitlen(ctx) <= key_bitlen);
}

int
Expand Down Expand Up @@ -609,15 +622,15 @@ cipher_ctx_get_tag(cipher_ctx_t *ctx, uint8_t *tag, int tag_len)
int
cipher_ctx_block_size(const mbedtls_cipher_context_t *ctx)
{
return mbedtls_cipher_get_block_size(ctx);
return (int)mbedtls_cipher_get_block_size(ctx);
}

int
cipher_ctx_mode(const mbedtls_cipher_context_t *ctx)
{
ASSERT(NULL != ctx);

return cipher_kt_mode(ctx->cipher_info);
return mbedtls_cipher_get_cipher_mode(ctx);
}

bool
Expand Down Expand Up @@ -652,7 +665,7 @@ cipher_ctx_reset(mbedtls_cipher_context_t *ctx, const uint8_t *iv_buf)
return 0;
}

if (!mbed_ok(mbedtls_cipher_set_iv(ctx, iv_buf, ctx->cipher_info->iv_size)))
if (!mbed_ok(mbedtls_cipher_set_iv(ctx, iv_buf, (size_t)mbedtls_cipher_get_iv_size(ctx))))
{
return 0;
}
Expand Down Expand Up @@ -714,7 +727,7 @@ cipher_ctx_final_check_tag(mbedtls_cipher_context_t *ctx, uint8_t *dst,
{
size_t olen = 0;

if (MBEDTLS_DECRYPT != ctx->operation)
if (MBEDTLS_DECRYPT != mbedtls_cipher_get_operation(ctx))
{
return 0;
}
Expand Down Expand Up @@ -866,7 +879,7 @@ md_ctx_size(const mbedtls_md_context_t *ctx)
{
return 0;
}
return mbedtls_md_get_size(ctx->md_info);
return (int)mbedtls_md_get_size(mbedtls_md_info_from_ctx(ctx));
}

void
Expand Down Expand Up @@ -936,7 +949,7 @@ hmac_ctx_size(mbedtls_md_context_t *ctx)
{
return 0;
}
return mbedtls_md_get_size(ctx->md_info);
return mbedtls_md_get_size(mbedtls_md_info_from_ctx(ctx));
}

void
Expand Down
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